Byung Chan Kim

Small wideband PIFA for mobile phones at 1800 MHz

A small PIFA applicable to mobile telephones is described. To minimize the volume of the antenna a tapered type patch with corrugation is employed. The antenna is designed using CST microwave studio and its characteristics are compared with a basic PIFA with similar volume. The obtained volume was less than 50% of a conventional 1/4 wavelength PIFA.

Tapered type PIFA design for mobile phones at 1800 MHz

In this paper, a new compact PIFA applicable to PCS system is described. The Principle aim in design is to broaden the bandwidth within limited body thickness of mobile phones. To overcome the narrow bandwidth characteristic that is typical of a patch antenna a type of tapered patch is employed. The antenna is designed using CST Microwave Studio and its characteristics are compared with a basic PIFA with similar volume. In specific case, bandwidth of about 15.2% was achieved experimentally.

Evaluation of RF electromagnetic field exposure levels from cellular base stations in Korea.

This article presents the measurement results of human exposure to CDMA800 and CDMA1800 signals at locations in Korea where the general public has expressed concern. Measurements were performed at 50 locations across the country to compare the electromagnetic field levels with the general public exposure compliance limits. At each site, the distances between the nearest single or co-located base station and measurement positions were within a range of approximately 32-422 m. The measured exposure levels were very low compared with the international standard and the Korean human protection notice. The highest field level was 1.5 V/m, which corresponds to 0.15% of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for human exposure.

Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on serum hormone levels in rats

Despite more than a decade of research on the endocrine system, there have been no published studies about the effects of concurrent exposure of radiofrequency electromagnetic fields (RF-EMF) on this system. The present study investigated the several parameters of the endocrine system including melatonin, thyroid stimulating hormone, stress hormone and sex hormone after code division multiple access (CDMA, 849 MHz) and wideband code division multiple access (WCDMA, 1.95 GHz) signals for simultaneous exposure in rats. Sprague-Dawley rats were exposed to RF-EMF signals for 45 min/day, 5 days/week for up to 8 weeks. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg (total 4.0 W/kg). At 4 and 8 weeks after the experiment began, each experimental groups 40 rats (male 20, female 20) were autopsied. Exposure for 8 weeks to simultaneous CDMA and WCDMA RF did not affect serum levels in rats of melatonin, thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxin (T4), adrenocorticotropic hormone (ACTH) and sex hormones (testosterone and estrogen) as assessed by the ELISA method.

Methods of evaluating human exposure to electromagnetic fields radiated from operating base stations in Korea

This article presents measurement methods used to determine the human exposure to electromagnetic fields radiated from operating base stations. In Korea, when evaluating the human exposure to electromagnetic fields from operating base stations, the measurement procedure is different between the following cases: in situ measurement and electromagnetic environment measurement. When performing an in situ measurement, compliance with human exposure limits is determined by the spatially averaged field value obtained within the space occupied by humans at one arbitrary position, but when performing an electromagnetic environment measurement, it is determined by the maximum value at the highest field position selected from several places.

The effects of exposure to 915 MHz radiofrequency identification on cerebral glucose metabolism in rat: A [F-18] FDG micro-PET study

Abstract Purpose: We investigated the effect of whole-body exposure to 915-MHz radiofrequency identification (RFID) on rat cortical glucose metabolism by using 18F-deoxyglucose positron emission tomography (FDG-PET). Materials and methods: Male Sprague-Dawley rats were divided into three groups: Cage-control, sham-exposed and RFID-exposed groups. Rats were exposed to the 915-MHz RFID for 8 h daily, 5 days per week, for 2 or 16 weeks. The whole-body average specific absorption rate (SAR) was 4 W/kg for the field of the 915 MHz RFID signal. FDG-PET images were obtained the day after RFID exposure, using micro-PET with a FDG tracer. With a Xeleris functional imaging workstation, absolute values in regions of interest (ROI) in the frontal, temporal and parietal cortexes and cerebellum were measured. Cortical ROI values were normalized to the cerebellar value and compared. Results: The data showed that the relative cerebral glucose metabolic rate was unchanged in the frontal, temporal and parietal cortexes of the 915 MHz RFID-exposed rats, compared with rats in cage-control and sham-exposed groups. Conclusion: Our results suggest that 915 MHz RFID radiation exposure did not cause a significant long lasting effect on glucose metabolism in the rat brain.

Effects of whole-body exposure to 915 MHz RFID on secretory functions of the thyroid system in rats.

As a part of an investigation on the potential risks of radiofrequency identification (RFID) on human health, we studied whether exposure to 915 MHz RFID in rats significantly affected the secretory function of the thyroid system. A reverberation chamber was used as a whole-body exposure system. Male Sprague-Dawley rats were exposed for 8 h per day, 5 days per week, for a duration of 2, 4, 8, or 16 weeks. The estimated whole-body average specific absorption rate (SAR) varied from 3.2 to 4.6 W/kg depending on the age/mass of the animals for the field of the 915 MHz RFID reader. Plasma levels of triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) were evaluated via enzyme-linked immunosorbent assay. Morphological changes in the thyroid gland were then analyzed. No changes in T3, T4, or TSH were observed over time between the sham- and RFID-exposed groups. We suggest that subchronic exposure to 915 MHz RFID at a SAR of 4 W/kg does not cause significant effects on thyroid secretory function.

Evaluation of radiofrequency exposure levels from multiple wireless installations in population dense areas in Korea

This paper presents the results of measurements from simultaneous human exposure to various radiofrequency (RF) signals at densely populated areas. Measurements were performed at 1260 positions across Korea to determine exposure compliance to electromagnetic fields for the general public. The measured exposure levels were very low compared with the international exposure guidelines and Korean human protection notice. The highest total exposure ratio was 5.1 × 10(-3) (approximately 7.1% of guideline limits).

Uncertainty Estimation for Evaluating Human Exposure Levels to RF Electromagnetic Fields from Cellular Base Stations

This paper investigates the estimation of uncertainty when evaluating the levels of human exposure to electromagnetic fields radiated from cellular base stations which aim to verify the exposure compliance with human protection guidelines. Uncertainty should be provided when publishing the results of an evaluation since measured physical quantities are not complete unless they are accompanied by some indication of their reliability. In this study, uncertainty sources are classified into four groups: physical parameters, mechanical constraints, postprocessing, and measurement equipment. Type A standard uncertainties are obtained from repeated observations by in situ measurement around cellular base stations, and they include uncertainties introduced by sources other than measurement equipment. Type B uncertainties are determined from the calibration data offered by measurement equipment manufacturers. The estimated overall uncertainty is ±3.82 dB.

Analytical Technique To Evaluate the Asymptotic Part of the Impedance Matrix of Microstrip Dipole On a Uniaxial Substrate - Abstract

The integral transform method with the asymptotic extraction technique is formulated to evaluate a Sommerfeld type integral for the analysis microstrip dipole on a uniaxial substrate. The infinite double integral of the asymptotic part of the impedance matrix with triangular subdomain basis function with edge condition can be reduced to a finite one-dimensional integral. This finite one-dimensional integral can be easily evaluated numerically after the singular part of the integral is treated analytically. It is demonstrated the efficiency and accuracy of the proposed method to evaluate the asymptotic part of impedance matrix.